Aquatic Ecosystems

Occupy largest part of biosphere Two major categories: Freshwater Marine

Aquatic Characteristics Vertical Stratification: Distinct vertical distribution of water density Based on variable such as light and temperature Light: absorbed by organisms and water; intensity decreases w/depth 2 zones based on light penetration: Photic: light penetrates; sufficient for photosynthesis Aphotic (profundal): very little light penetrates; insufficient for photosynthesis Temperature: Light-penetrated layer: warmed by heat energy of sunlight Thermocline: narrow zone of rapid temperature change; separates uniform warm upper layer and cold deeper waters Deep Water (Benthic zone): bottom of any aquatic ecosystem

Freshwater Salt concentration of < 1% Characteristics influenced by: Patterns and speed of water flow Climate of area 2 categories: Standing: Lakes, ponds, inland wetlands Moving: rivers, streams

Standing Freshwater: Lakes Lakes: Large, natural bodies of standing fresh water Productivity determined by: temp, depth, nutrient content, and dissolved oxygen content Consist of 4 zones: littoral, limnetic, profundal, and benthic

Standing Freshwater: Wetlands Wetlands: Area covered with water at some point in the year Can also be saltwater among the richest of ecosystems – very diverse Serve as: Water-storage basins and help reduce intensity of flooding Filters which improve water quality - “nature’s kidneys”

Moving Freshwater: Rivers and Streams Bodies of water moving continuously in one direction Nutrient content largely determined by terrain & vegetation through which it flows Empty into oceans at estuaries Salinity varies One of most productive due to nutrients from river Crucial feeding areas for many types of water fowl

Marine Salt concentration of ~ 3% Covers ~ 75% of the earth’s surface Impact climate Evaporation of seawater provides most rainfall Ocean temps affect wind patterns Supply a good portion of world’s oxygen Consume large amount of atmospheric carbon dioxide Communities distributed through 5 general zones

Marine Zones Intertidal – where land meets water submerged and exposed due to tides Neritic – past intertidal; shallow region over continental shelves includes coral reefs Oceanic pelagic – extends past continental shelves can be very deep (open water); includes most of ocean’s water water constantly mixed by ocean currents

Marine Zones Benthic – ocean bottom; below neritic and oceanic pelagic zones nutrients “rain” down from above as detritus Abyssal zone – very deep benthic communities organisms adapted to continuous cold, high pressure, little to no light, and low nutrients deep-sea hydrothermal vents found here (chemoautotrophs!)

Brackish Water part salty, part fresh mix found where the two meet in such places as estuaries, deltas and mangrove swamps. also found on the surface layer of the Baltic and Black Seas, where the salt water is diluted by the many freshwater courses that pour into them. conditions are optimal for neither freshwater or marine creatures - often lack diversity.